JP3341531B2 - Rocker arm made of high-strength Fe-base cast alloy - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to a rocker arm made of a base cast alloy.

[0002]

2. Description of the Related Art Conventionally, since a rocker arm, which is a structural member of an internal combustion engine, is required to have strength, toughness, and wear resistance, an Fe-based cast alloy having these characteristics has been used. Further, as a rocker arm made of an Fe-based cast alloy having these characteristics, for example, Japanese Patent Application Laid-Open No.
As described in JP 11941, weight% (% by mass)
[Hereinafter,% indicates weight% (mass%)], C: 2 to 4%, Cr: 10 to 25%, Mo: 1 to 10%, Si: 0.1 to 2%, Mn: 0.1 to 2%. Fe-based casting containing 1 to 2%, Co: 0.1 to 2%, W: 0.1 to 2%, Ni: 0.1 to 3%, with the balance being Fe and inevitable impurities. Rocker arms made of an alloy are known.

[0003]

On the other hand, with the recent increase in output and weight of the internal combustion engine, the rocker arm has also been required to be smaller and thinner. Many rocker arms, such as a rocker arm made of a cast alloy, have excellent toughness and wear resistance, but do not have sufficient strength, and thus cannot satisfy these requirements satisfactorily.

[0004]

Means for Solving the Problems Accordingly, the present inventors have
In particular, focusing on the rocker arm made of the conventional Fe-based cast alloy described above, as a result of conducting research to improve the strength thereof,
As shown in FIG. 2, the Fe-based cast alloy constituting the rocker arm made of the conventional Fe-based cast alloy has a relative crystallized during casting, as exemplified by a micrograph of a structure photograph (magnification: 500 times) obtained by a metallurgical microscope. It has a structure in which massive eutectic carbides and needle-like precipitated carbides formed by heat treatment of quenching and tempering are dispersed and distributed in a martensitic matrix. The Fe-base cast alloy contains N and B components as alloy components. Then, the N component and the B component are crystallized and precipitated as a eutectic carbonitride and a precipitated carbonitride, and the longitudinal length of the eutectic carbonitride and the precipitated carbonitride is Research results have shown that the fineness is as small as 50 μm or less, which significantly improves the strength.

[0005] The present invention has been made based on the above research results, C: 2 to 4%, Si: 0.1 to 2%, Mn: 0.1 to 2%, Cr: 10 to 10% 25%, Mo and / or W: 0.1 to 10%, N: 0.01 to 1%, B: 0.001 to 0.1%, and if necessary, Ni and / or Co: 0.1 to 5%, with the balance consisting of Fe and unavoidable impurities, and a martensitic matrix having a eutectic carbonitride and a precipitated carbonitride having a longitudinal length of 50 μm or less. It is composed of an Fe-based casting alloy having a structure in which boride is dispersed and distributed,
F with high strength and excellent toughness and wear resistance
It is characterized by a rocker arm made of e-base cast alloy.

Next, the reason why the component composition of the Fe-based cast alloy constituting the rocker arm of the present invention is limited as described above will be described. (A) C In addition to improving the strength by partially forming the base martensite, the C component has a length in the longitudinal direction without forming needle-like precipitated carbides that cause a decrease in strength. In any case, the effect of forming a precipitated carbonitride and a eutectic carbonitride of 50 μm or less, desirably 30 μm or less, and improving wear resistance without lowering the high strength provided by the martensite matrix. However, if the content is less than 2%, the desired effect cannot be obtained in the above-mentioned action,
On the other hand, if the content exceeds 4%, the toughness decreases, so the content is 2 to 4%, preferably 3 to 4%.
It was determined to be 3.6%.

(B) Si In addition to the deoxidizing action, the Si component has the action of increasing the fluidity of the molten metal and improving the castability. If the content is less than 0.1%, the Si component is not desirable. Is not obtained, while if the content exceeds 2%, the toughness decreases. Therefore, the content is set to 0.1 to 2%, preferably 0.5 to 1.5%. Was.

(C) Mn The Mn component has an effect of improving the toughness by forming a solid solution in the base material in addition to a deoxidizing effect. On the other hand, if the content exceeds 2%, the abrasion resistance decreases, so the content is 0.1 to 2%, preferably 0.4 to 2%.
It was determined to be 1.1%.

(D) Cr The Cr component has an effect of forming a carbonitride with Mo and W, and also N and B components to improve wear resistance. If the desired effect is not obtained, the toughness will be reduced if the content exceeds 25%.
-25%, preferably 15-20%.

(E) Mo and W These components form a eutectic carbonitride and a precipitated carbonitride as described above to improve wear resistance.
There is an effect of improving the strength by forming a solid solution in the base material, but if the content is less than 0.1%, the desired effect cannot be obtained, whereas if the content exceeds 10%, the toughness is reduced. Therefore, the content was determined to be 0.1 to 10%, preferably 1 to 5%.

(F) NN As described above, the NN component forms a eutectic carbonitride and a precipitated carbonitride having a longitudinal length of 50 μm or less, preferably 30 μm or less together with the component B to form a martensite. It has the effect of improving the wear resistance without impairing the high strength provided by the site substrate, but its content is N: 0.0
If it is less than 1%, in particular, the length of the precipitated carbonitride or the carbonitride exceeds the length of 50 μm, and the desired high strength cannot be secured. If the amount exceeds 1%, the toughness will decrease. Therefore, the content is set to 0.01 to 1%, preferably 0.2 to 0.6%.

(G) BB In the B component, as described above, a eutectic carbonitride and a precipitated carbonitride are formed together with the N component to improve wear resistance and to refine crystal grains. It has the effect of improving the strength, but if its content is less than 0.001%, the desired effect cannot be obtained, whereas if its content exceeds 0.1%, the toughness will decrease. From 0.001 to 0.1%, preferably 0.01 to 0.08
%.

(H) Ni and Co Since these components have a function of dissolving in the base material to promote martensitic transformation and thereby further improving the strength, they are contained as necessary. Quantity is 0.1
If the content is less than 5%, the desired effect of improving the effect cannot be obtained. On the other hand, if the content exceeds 5%, no further effect of improving the strength can be obtained. 1-5
%, Preferably 1-3%.

The longitudinal length of the eutectic and precipitated carbonitride in the Fe-base cast alloy constituting the rocker arm of the present invention is basically adjusted by the content of the N component as described above. However, if the length exceeds 50 μm, the strength sharply decreases and a desired high strength cannot be ensured. Therefore, the length in the longitudinal direction is set to 50 μm or less, preferably 30 μm or less.

[0015]

Next, a rocker arm made of an Fe-based cast alloy according to the present invention will be described in detail with reference to examples. Using a conventional high-frequency melting furnace, a Fe-base alloy melt having the component composition shown in Table 1 was prepared, cast into a lost wax mold, allowed to cool, and then held at 900 ° C. in the atmosphere for 1 hour, followed by oiling. 3A is a front view, and FIG. 3B is a bottom view. And a rocker arm made of an Fe-based cast alloy of the present invention having a length of 45 mm (hereinafter referred to as the rocker arm of the present invention) 1
To 7 and conventional rocker arms made of a Fe-based cast alloy (hereinafter referred to as conventional rocker arms) 1 to 13, respectively.

Next, as shown in the schematic explanatory view of FIG. 4, these rocker arms are fitted with a bent tip portion of a C-shaped fixing tool in a recess formed at the tip end of the bottom surface of the rocker arm, as shown in FIG. 4. A load was applied to the other end of the bottom surface of the rocker arm from above at a speed of 23 kgf / sec, and a static destruction test was performed to measure the load (breaking load) when the rocker arm was broken, and the strength was evaluated based on the measurement results. . Table 2 shows the results. Further, for these rocker arms, Charpy impact value and Rockwell hardness (C scale) were measured to evaluate toughness and wear resistance. The results of these measurements are also shown in Table 2.

[0017]

[Table 1]

[0018]

[Table 2]

[0019]

From the results shown in Tables 1 and 2, the rocker arms 1 to 7 of the present invention have excellent toughness (Charpy impact value) and wear resistance equivalent to those of the conventional rocker arms 1 to 13, and It is clear that it has a higher strength than this. As described above, the rocker arm made of an Fe-based cast alloy according to the present invention has high strength, and is also excellent in toughness and wear resistance. Can be done.

[Brief description of the drawings]

FIG. 1 is a schematic structural view showing a typical structure of an Fe-based cast alloy constituting a rocker arm made of a conventional Fe-based cast alloy.

FIG. 2 is a front view (a) and a bottom view (b) of a rocker arm.

FIG. 3 is a schematic explanatory diagram of a rocker arm static breakdown test.

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁷ Identification code FI F01L 1/18 F01L 1/18 M (56) References JP-A-48-19421 (JP, A) JP-A-6-200354 ( JP, A) JP-A-5-279809 (JP, A) JP-A-59-211553 (JP, A) JP-A-63-290243 (JP, A) JP-A-6-220573 (JP, A) JP JP-A-2-64210 (JP, A) JP-A-63-303030 (JP, A) JP-A-2-149638 (JP, A) JP-A-60-234947 (JP, A) (58) Fields investigated (Int) .Cl. ⁷ , DB name) C22C 37/08 C22C 37/00 C22C 38/00 302 C22C 38/38 C22C 38/58 F01L 1/18

Claims (2)

(57) [Claims] 1. wt% (mass%): C: 2 to 4%, Si: 0.1 to 2%, Mn: 0.1 to 2%, Cr: 10 to 25%, Mo and / or W : 0.1 to 10%, N: 0.01 to 1%, B: 0.001 to 0.1%, the balance being Fe and inevitable impurities, and martens A high-strength Fe-base alloy comprising a Fe-base cast alloy having a structure in which a eutectic carbonitride having a longitudinal length of 50 μm or less and a precipitated carbonitride are distributed and distributed on the site substrate. Rocker arm made of cast alloy. 2.% by weight: C: 2 to 4%, Si: 0.1 to 2%, Mn: 0.1 to 2%, Cr: 10 to 25%, Mo and / or W: 0.1 -10%, N: 0.01-1%, B: 0.001-0.1%, Ni and / or Co: 0.1-5%, the balance being Fe And an Fe-based cast alloy having a structure in which a eutectic carbonitride having a longitudinal length of 50 μm or less and a precipitated carbonitride were dispersed and distributed on a martensite base and a martensite base. A rocker arm made of a high-strength Fe-based cast alloy, characterized in that: